The purpose of this investigation is to study the regulation of intracellular protein degradation in Escherichia coli. In an effort to obtain cell-free preparations that proteolyze specific enzymes, extracts of E. coli were made by gentle disruption of cells with lysozyme-EDTA. Such extracts catalyze the degradation of added purified glutamine synthetase, as well as other purified proteins, and represent a proteolytic artifact due to lysozyme. This lysozyme-induced proteolysis has been studied using E. coli glutamine synthetase in order to characterize the essential features of protein-protein interaction required for hydrolysis. In addition, studies on intracellular degradation in E. coli have continued. Partial degradation of added purified glutamine synthetase has been demonstrated in cell-free extracts derived from catalase-deficient mutants, and these mutants represent a potential source for isolation and characterization of an intracellular degradation system in E. coli. Techniques used in these studies have included polyacrylamide pore gradient electrophoresis, isotopic labeling, chromatographic techniques, autoradiography, and enzymatic assay of functional proteins.